Flatt and Scruggs were born Lester Flatt and Earl Scruggs. Those aren't stage names. They met as members of Bill Monroe's band, the Blue Grass Boys, in 1946. They stayed with Bill for two years before striking it out on their own as the Foggy Mountain Boys. The group was named for the Carter family tune "Foggy Mountain Top."
Their first home was on WDVA-AM in Danville, VA in 1948. They stayed less than three months and moved on to Earl's home state at WHKY-AM, in Hickory, North Carolina. They picked up Jim Shumate on fiddle and Mac Wiseman to sing. Wiseman was actually a DJ from WSVA-AM. As a 4-piece they joined the "Farm and Funtime" Program on WYCB-AM in Bristol, Tennessee. In four weeks they sold 10,000 song books through the mail. That scored them their first record deal. They stayed with Mercury Records and WYCB-AM for another 3 years.
The next stop was The Old Dominion Barn Dance on WRVA-AM in Richmond. the program was syndicated on CBS. It was after this in 1955 that The Grand Ol' Opry caved in and they were at last invited to appear. Bill Monroe didn't want them on, but the public pressure, and more specifically the pressure from sponsor Martha White Flour sealed the deal.
Scruggs has the longer radio resume of the two. Lester made his radio debut on WDBJ-AM in Roanoke, VA in 1939, and played with the Allied Kentuckians on WNOX-AM in Knoxville. And yes.. he even played on WSM-AM.. just not the Oprey.